The present invention provides improvements in changeable signs. One of the inventors of this application, Fred. M. Black, is the inventor of U.S. Pat. No. 4,761,905 entitled "Scanned Electromechanical Display" and U.S. Pat. No. 4,912,442 entitled "Scanned Electromechanical Alphanumeric Display Apparatus". Two of the co-inventors of this application, Fred. M. Black and G. Frank Dye are the co-inventors of U.S. Pat. No. 5,412,891 entitled "Changeable Sign". The disclosures of these three patents are hereby incorporated herein by reference. The '905 and '442 patents provide a description of certain of the prior art in the field of the present invention. Additional improvements are disclosed in Application Ser. No. 08/761,125, filed Dec. 6, 1996, based on Provisional Application Ser. No. 60/008795, filed Dec. 18, 1995, both of which are incorporated herein by reference.
The cited patents and applications disclose sign elements which can display alphanumeric or graphical information, through the selective arrangement of individual pixels. The pixels are rotatably mounted elements having multiple display faces, only one of which is noticeable to an observer at a time. The overall pattern of pixel display faces comprises the alphanumeric or graphical indicia of the sign. These prior patents disclose arrays of such pixels and actuator devices which pass behind the arrays to selectively rotate the pixels, causing a new display face of a rotated pixel to be noticeable and, thus, changing the displayed indicia of the sign. The present invention has these notions in common, but provides improved design features to create a superior product.
More specifically, the '442 patent disclosed a display apparatus having a plurality of rotationally mounted display elements that are arranged into a grid matrix of rows and columns, each display element having first and second display faces perpendicular to each other and joined along respective adjacent edges. Each display element also has first and second ramp surfaces rigidly connected along inside edges of and extending substantially away from a back surface of the first and second faces. The display apparatus includes a series of solenoids. which strike the ramp surfaces of the display elements, causing the display elements to rotate 90 degrees. The solenoids are mounted on a carriage that moves bidirectionally on a horizontal path behind the display apparatus. The electronics controlling the solenoids in the '442 apparatus cause the solenoids to fire and release for each pixel.
The shape and mounting of the pixels was a major improvement introduced by the '891 patent. The display faces were designed to be cylindrically concave, with the axis of concavity being parallel to the pixel's axis of rotation. Also, the ramp surfaces were given different configurations. These modifications allowed the pixels to be arranged in closer proximity to one another and greatly enhanced the performance of scanned pixel signs.
Periodically, one or more of the pixels may jam during operation of the sign. When a pixel jams, the rigid solenoid plunger or reset pin used to set or reset the pixel is unable to move the pixel and the result is damage to the sign. When the jammed pixel and the plunger or reset pin make contact as the carriage speeds by. something must give. Either the plunger or reset pin is bent or the jammed pixel is broken. In certain situations, the carriage may be damaged or knocked off track. If the plunger or reset pin is bent, the operation of an entire row of pixels is affected. Furthermore, the bent plunger or reset pin may cause additional damage or pixel jamming. The damage to the sign and costs to repair it are expensive and commercially undesirable.
Thus, there exists a need for a scanned pixel sign having solenoids and reset pins that prevent damage to themselves or the sign if the pixels become jammed.